Aerodynamic vehicles, such as aircraft, guided missiles, munitions, and unmanned aerial vehicles, include design parameters that are configured to provide the necessary lift and control to overcome the drag and weight of a vehicle during flight. For example, the aspect ratio (“AR”), the lift coefficient, and the drag coefficient are examples of typical design parameters which affect the performance of an aerodynamic vehicle.
One goal in designing an aerodynamic vehicle is to maximize the lift generated by the aerodynamic surfaces for the drag associated with the overall aerodynamic vehicle design, i.e., maximize the lift to drag (“L/D”) ratio. In pursuit of this goal, the AR is considered an important parameter and can be computed as follows:AR=(span)2/area
wherein the span is the distance from wingtip to wingtip and area is the surface area of the wings.
The AR is an important design parameter because, generally, a wing's ability to generate lift is influenced by changes in aspect ratio. As aspect ratio increases for a given wing design the lift generating capability also increases. Wings with high aspect ratios are more suited for missions requiring long flight times or long distance glide range whereas wings with lower aspect ratio are more suited for missions requiring higher speeds and long distance cruise ranges.
For many aerodynamic vehicles, especially guided missiles, munitions, and unmanned aircraft, variable geometry wings may conflict with other desirable design parameters, such as reduced physical envelope, launch constraints, and/or compact storage (dense packing). One attempt to reconcile these competing interests is taught in U.S. Pat. No. 5,615,846 (the “846 patent”), which is incorporated by reference herein in it entirety, where extended range and increased maneuverability are accomplished through deployable joined wings. During storage and launch, the deployable wings remain tucked against the fuselage of the guided missile, conserving storage space. The deployable wings change geometry and deploy into a diamond shaped joined wing configuration during flight, in some cases tripling the range of an un-powered munition/ordinance or missile. While, the '846 patent effectively combines the advantages of compact storage and deployable wings, the deployed joined wings do not alter the AR of the aerodynamic vehicle during flight for different mission parameters.
Other attempts at variable wing geometries have included telescoping wings that alter the aerodynamic characteristics of the airframe. Previous aerodynamic vehicles using telescoping wings employ a conventional cantilevered wing configuration, where the extending wing provides a means for manipulation of the wings aspect ratio. Unfortunately, cantilevered wings are typically large and heavy and lack the ability to fold or package in a compact and streamlined stowed configuration.
The mechanical complexities of implementing deployable wing systems in a reduced physical volume have prevented a compact arrangement of flight control schemes. Prior attempts to include deployable wings for guided munitions and other flight vehicles have resulted in flight control actuation schemes that, in the case of air launched and ground launched guided munitions, are housed outside of the wing structure. The control actuators are often mounted on the fuselage, for example. Conventionally, when actuation of a control surface on a deployable wing has been required, the means for actuating the deployable control surfaces are complicated due to the mechanical transmission of actuation forces across or through the articulated joints between the fuselage and the wing panels. As such, the aerodynamic control surfaces on deployable wings have suffered from increased part counts, increased cost and reduced reliability.